$A$ and $B$ are $20 \text{ km}$ apart. $A$ can walk at an average speed of $4 \text{ km/hr}$ and $B$ at $6 \text{ km/hr}$. If they start walking towards each other at $7 \text{ a.m.}$,when will they meet? (in $\text{a.m.}$)

Mohan walks from Tilak Nagar to Moti Nagar and back in a certain time at the rate of $3 \frac{1}{2} \, km/h$. But,if he had walked from Tilak Nagar to Moti Nagar at the rate of $3 \, km/h$ and back from Moti Nagar to Tilak Nagar at the rate of $4 \, km/h$,he would have taken $10 \, minutes$ longer. The distance between Tilak Nagar and Moti Nagar is (in $km$)

$A$ $570 \, m$ long train crosses a platform of equal length in $15 \, s$. What is the speed of the train in $m/s$?

$A$ horse rider travels on horseback from Bhopal to Chandigarh at a constant speed. If the horse increased its speed by $6 \, km/h$,it would take the rider $4 \, hours$ less to cover that distance. If the horse travelled at a speed $6 \, km/h$ lower than the initial speed,it would take him $10 \, hours$ more than the time he would have taken if he had travelled at a speed $6 \, km/h$ higher than the initial speed. Find the distance between Bhopal and Chandigarh in $km$.

In a flight of $600 \, km$,an aircraft was slowed down due to bad weather. Its average speed for the trip was reduced by $200 \, km/hr$ and the time of flight increased by $30 \, minutes$. The duration of the flight is (in $hour$):

Excluding stoppages, the speed of a bus is $54 \, km/h$ and including stoppages, it is $45 \, km/h$. For how many minutes does the bus stop per hour?